|In the electric stone age my attempts to apply this technology was just that - stony. The first attempt in 1991 with the then popular Speed 600 motor took only as far as to the first loop. This was the last manoeuvre for the airplane. The second attempt with a new airplane and a somewhat more powerful but much more expensive motor was a considerable improvement, but still a far cry from what we expect from a stunt model. I know of only one other person ( Urs Stalder, Switzerland) who at that time came closer to what we call control line aerobatics - but only up to the Square Eight. Then most of the energy left the airplane because the battery was empty. So I gave up on this frustrating power system.|
|In the meantime the world has changed drastically. With the advent of brushless motors and Lipo batteries this technology has caught up with IC power, and quite convincingly, at that. As we have recently|
e ven on international level ( World Championships and US Nationals) the
electric drive has proved itself fully competitive and on a par with IC
competition. Surely it will find still more widespread use in the future
everywhere. I felt like giving it another try.
Being a total electric layman my abilities in this area don’t reach much further than turning the light switch on and off. So it should be helpful to ask for some competent advice from more knowledgeable individuals. As luck would have it at that time Christoph Holtermann didn’t want to continue work with his smaller electric model and he offered me his equipment, which consisted of the Strecker 295.15 motor, Graupner Compact Control 40 controller, JMP timer, and APC 11x5,5 E propeller. He had built one of my profile designs (which he feels is a capable stunt model) for the OS 35 and later converted to electric drive with these components. Only thing I had to do was to build a model and install Christoph’s equipment.
I have absolutely no intention to enter the contest circle with an electric system (I still prefer to listen to my softly purring ST 60). I just wanted to have a go and try out an electric variation. A simple profile model was all that was needed for this task. I decided to build a similar airplane as Christoph did (for those interested you can find more information about the model on my Me 109 page). It was constructed almost exactly as shown on the original drawing. The only modifications were made to the fuselage nose (motor mounts) and the undercarriage (for looks!). I will add only a few hints concerning those details which differ from usual construction ways.
landing gear wire is not mounted to the fuselage. For optical reasons it
is anchored in the wing, but close to the fuselage ( like on the original
aircraft). Since this is not far away from the bellcrank mount, some brainwork
offered the idea to combine both the bellcrank mount and gear mount into
one unit. This should make for a very stout central unit in a place where
the highest loads appear. This part integrates three central ribs and must
be built as a whole unit before beginning wing construction.
Fuselage nose construction differs only slightly from normal. Long engine bearers are not required. Instead we add two short hardwood bearers which contain a M3 (4/40) threaded insert each. These inserts will hold the front fibre glass ring which is used for front mounting the motor. If a spinner is desired an additional balsa front ring is required to fill the gap between the fuselage nose and the spinner back plate. There’s a roomy fuselage cut out for the battery and a big air scoop to cool down any undesired battery temperature grades (some original 109s had a distinctive air scoop there). In the fuselage center sheet some small hardwood blocks were added to allow solid fixing of U-bolts for mounting the battery, the controller, and the timer.
choice of finish is up to you. My electric 109 version came out a little
heavier than desired (as usual; the military paint scheme requires more
than one colour coat). Christoph's airplane had come out at 1060 Gramm with
an OS LA 46, but 1200 (42,3 oz) in the electric version (so I need not be
ashamed so much about MY product). If a perfect finish is not required a
lot of kilos/ pounds can be saved. The chosen drive system is just right
for this size of airplane, so it’s not possible to save weight here.
The only area which deserves high attention is the propeller. So far I’ve
tested several brands and sizes ( 6 different props). In my opinion I’ve
got the best “feelings” from the Zinger wood 11 x 6 W and the
APC 12 x 6 cut to almost 11 diameter. The results are given in the table.
If another motor is desired the AXI 2820/12 should be a suitable replacement.
It has some 15 gramms more.
|This airplane was never meant to be a “top gun” beater. Instead it should serve as a suitable stunt trainer in the typical Nobler size (which I feel is a most practical tool for this purpose) for the advanced stunt flyer - in the electrical field. It is easy and quick to build, can be built light, but yet has the performance required to perform a respectable FAI or AMA schedule. This design together with the electric equipment may serve as a base point into electrical adventures for a beginner in this field.|
|Much better electric stunt models have already been used in control line circles, and very successfully, at that. What I intended to show is a very basic setup which has already proved successfully, can help to enter the electric arena, and doesn’t cost you a fortune. The components are commercially available easily, help is readily available, and the system-inherent benefits are for free. Some tables are added which specify the details of the model, the motor, and the props.|
details to the test flights. Flight time was set to 5,5 minutes.
1) was a flight with a small prop to be on the safe side.
2) with recommended APC prop; okay, power not fully convincing.
3) Almost okay; slight power drop near end of flight.
4) No power.
5) Power drop after Horizontal Eight; motor hot (shortly touchable).
6) Slight power drop after Vertical Eight; motor slightly hot
All flights were made in warm weather and just the slightest touch of wind. Except for flight 1 and 4 power was adequate but not overwhelming. This can be attributed to the weight of the model. After all 1220 Gramm are a little overweight for a Nobler size airplane.
I’ve already fully enjoyed the benefits of this drive system. Once the first hurdles are overcome, flying electric has some pleasant surprises for us. Only one problem: I’ll have to break myself of the habit to run after the paper cleaning towels after each flight !
I've attached some more photos. Just hit the button!